There exist numerous portions of the human body, such as fingerprints and toeprints, retina patterns of the eyes, facial features, blood vessel patterns, and similar, enabling differentiation among human beings. With advances in biometrics technology in recent years, various devices have been provided which recognize features of body parts, which are such portions of the human body, and perform authentication of individuals.
For example, comparatively large quantities of individual characteristic data can be obtained from blood vessels in the palms and backs of the hands and the fingers as well as from palmprints, so that such data is useful to ensure reliability of individual authentication. In particular, the patterns of blood vessels (veins) remain unchanged from infancy throughout life, and are thought to be unique to each individual, making them appropriate for use in individual authentication. In such individual authentication devices, during registration or authentication, the user brings the palm of a hand close to an image capture device. The image capture device emits near-infrared rays, which are incident on the palm of the hand. The image capture device uses a sensor to receive near-infrared rays which have reflected from the palm of the hand.
Hemoglobin in the red corpuscles flowing in the veins has lost oxygen. This hemoglobin (reduced hemoglobin) absorbs near-infrared rays at wavelengths near 760 nanometers. Consequently when near-infrared rays are made incident on the palm of a hand, reflection amount is reduced only in the areas in which there are veins, and the intensity of the reflected near-infrared rays can be used to identify the positions of veins.
The user first uses an image capture device to register vein image data of the palm of his/her hand in a server or on a card. Then, in order to perform individual authentication, the user employs an image capture device to cause the vein image data of his/her hand to be read. The registered vein image retrieved using a user ID is verified against the vein pattern of the vein image for verification thus read, and individual authentication is performed (see for example Japanese Patent Laid-open No. 2004-062826 (FIG. 2 through FIG. 9)).
In detection of biometrics information without contact, the body part can freely move relative to the image capture device, and in particular the hand can be moved freely. On the other hand, the portion of the body for detection must be positioned within the region of image capture of the image capture device in order to enable precise detection. As such methods, when judging that a precise image capture may not be obtained by detected result of the hand position and orientation each time, a method has been proposed in which a display or voice is used to indicate that the hand position or orientation is inappropriate (see for example WO04/021884 (FIG. 3) and Japanese Patent Laid-open No. 2006-42880 (FIG. 11)). When using such methods, because there is no contact, accurate biometrics information can be detected even when performing detection in which there is no sense of resistance.
In non-contact detection of biometrics information, detection is performed without contact, and moreover the body part, and in particular the hand, moves freely. On the other hand, in order to perform biometrics authentication rapidly, numerous images must be captured, and appropriate images must be detected and output to the authentication process.
In the prior art, only past information for body part (hand) image capture is used to decide guidance messages, so that inappropriate messages are sometimes displayed while the user is moving the body part to the normal position. For example, in capture images of the palm of the hand as described above, a “please move your hand closer” message may be displayed while the hand is being brought close to the image capture region; or, a “please move to the right” message may be displayed while moving from the left to the right relative to the center of the image capture region.
Further, when the user moves his hand or other body part according to a displayed guidance message, there is the possibility that contradictory guidance messages are displayed in alternation, so that a situation occurs in which the user does not know how he should move his hand. For example, the messages “please move to the right”, “please move to the left”, “please move to the right” may be displayed in alternation, causing the user to become confused.